1. Field of the Invention
This invention relates to a vehicle door structure for improving the tone quality of a reproduced sound from a loudspeaker.
2. Description of the Related Art
Generally, audio equipment is installed on a vehicle, and an occupant can hear a sound, generated by the audio equipment, from a loudspeaker provided in a door device or the like. This loudspeaker is mounted via a bracket or the like in a loudspeaker mounting hole formed in a door inner panel of the door device. Such a conventional vehicle door structure is disclosed, for example, in Japanese Unexamined Patent Publication No. 2005-26817.
The door device has a double structure having an internal space formed by the door inner panel and a door outer panel. In this internal space, devices such as a window glass and an elevating device for elevating and lowering the window glass are accommodated, and a harness connected to these devices is wired. Thus, a plurality of service holes for mounting and equipping the different devices are bored in different sizes in the door inner panel.
If the loudspeaker is mounted on the conventional vehicle door structure, however, the above-mentioned service holes remain open, and the rigidity of the surroundings of the loudspeaker is insufficient. Thus, the essential performance of the loudspeaker cannot be exhibited, or a sound radiated into a vehicle compartment through the service hole interferes with a direct sound from the loudspeaker, thereby deteriorating tone quality. It may be conceivable to provide no service holes, but this is not a realistic measure from the points of view of maintainability, cost and weight.